Chapter 3 Normal Pregnancy

Chapter3 Normal pregnancy

Wang Fu-ling

一、 Pregnancy physiology  Pregnancy

is the maternal condition of

having a developing fetus( 胎儿 ) in the body.

What is pregnancy? Pregnancy is defined as the course of embryo （胚胎） and fetal growth and development in uterine It begain at the fertilization and end the delivery of the fetal and it’s attachment

（一） The fetus 1

Fetus growth and development  2 Fetal physiology

1 、 Fetus growth and development Fertilization is defined as the course of combination of the oocyte and sperm It onset 12h after ovulation usually in ampulla of the oviduct(fallopian tube)

1 、 Fetus growth and development  The

human conceptus from fertilization through the eighth week of pregnancy is termed an embryo from the eighth week until delivery ， it is a fetus.  The estimated age of the fetus calculated from the frist day of the last menstrual period ,assuming a 28-day cycle.

1 、 Fetus growth and development  During

the frist 8 weeks,the term embryo is used to denote( 表示 ) the developing organism because it is during this time that all the major organs are formed .

1 、 Fetus growth and development  After

the eighth week, the word fetus is proper, the growth of the fetus may be described in units of 4 weeks’ gestational age, beginning with the first day of the LMP （ last menstrual period ）

1 、 Fetus growth and development  8weeks:

the organs are beginning to form  12weeks: the fingers and toes have nails,and the external genitalia may be recognizable  16weeks :the sex is discernible as male or female  20weeks :heart tones may often be detected by stethoscope( 听诊器 ),movements have been perceives by mother,the uterine fundus is near the level of the umbilicus （脐）

1 、 Fetus growth and development  24weeks ：

some fat is beginning to be deposited beneath the wrinkled skin,viability is reached by the 24th week,but survival at this stage is still relatively rare  28weeks ： the lungs are now capable of breathing,but the surfactant content is low;survival is possible in level II or level III neonatal centers

1 、 Fetus growth and development  32weeks ：

if born at this stsge,about 5 of 6 infants survivie  36weeks ： the skin has lost its wrinkled appearance,the chances for survival are good  40weeks ： the head has a maximal transverse diameter of 9.5cm. The average fetus ,therefore,requires cervical dilatation of almost 10cm before it can descend into the vagina

2 、 Fetal physiology Contents:  Circulatory function  Hematology( 血液学 )  Respiratory function  Gastrointestinal function  Renal function  Endocrinology( 内分泌学 )

2 、 Fetal physiology （ 1 ） Circulatory function 2) fetus ←→placenta←→ mother 3) Umbilical cord: 1 umbilical vein (full of oxygen), 2 umbilical artery (lack of oxygen) 4) Mixed blood (vein and artery)

Development of embryo and fetus

2 、 Fetal physiology （ 2 ） Hematology （血液学） Erythropoiesis （红细胞生成） From yolk sac （卵黄囊） : 3 weeks From liver: 10 weeks From bone marrow and spleen ： after 10 weeks

*By10weeks the liver assumes the major role in erythropoiesis,but the spleen and bone marrow gradually take over this function

2 、 Fetal physiology (3) Respiratory function gas exchange in the fetus occurs in the placenta (4) Gastrointestinal tract No truly function until after birth (5) Kidney Its function begins at 9-12th week

2 、 Fetal physiology (6)Endocrinology •

Fetal thyroid: the first endocrine gland (6th week), synthesize thyroxine at 12th week

•

Fetal adrenal cortex consists mainly of a fetal zone that disappears about 6months after birth.

3 、 The placenta ， umbilical cord and amniotic fluid  The

placenta  The umbilical cord  The amniotic fluid （羊水）

（ 1 ） The placenta  Development

of the placenta  Functions of the maternal placental-fetal unit

（ 1 ） The placenta Structure 2. Primary villus （绒毛） 3. Secondary villus 4. third class villus fetal capillary( 胎儿毛细血管 ) enter the stroma 

*1 、 Development of the placenta  Fertilization 3. Place: oviduct (ampulla) 4. Process capacitation → acrosome reaction→ penetrate the zona pellucida→ second meiosis →zygote( 受精卵 )

Implantation 2. requirement • Disappear of •

zona pellucida Formation of syncytiotrophoblast

Synchronized development of blastocyst and endometrium • Adequate progesterone •

1. •

•

Process morula (day 3) → enter uterine cavity (day 4) → early blastocyst→ late blastocyst (day 6-7) → implantation location→ adherence→ penetration

（ 2 ） Functions of the maternal placental-fetal unit  Endocrine

function Human chorionic gonadotropin （ HCG ） Human chorionic somatomammotropin Placental proteins （胎盘蛋白） Estrogen  Metabolitic function  Protective function

Endocrine function Human chorionic gonadotropin(HCG)  It

is a glycoprotein that has biologic and immunologic similarities to luteinizing hormone from the pituitary  H CG is produced by the syncytiotrophoblast of the placenta  This measurement is useful because it can detect pregnancy in all patients on day 11 after fertilization

Endocrine function Human chorionic somatomammotropin(hGS)  hGS is a protein hormone with immunologic and biologic similarities to pituitary growth hormone  It has been suggested that hGS is the “growth hormone”of pregnancy

Endocrine function Placental proteins  PAPP-A,PAPP-B,PAPP-C,PAPP-D  PAPP-D is the hormone hCS

Endocrine function Estrogen  Estrogen production by the placenta is dependent upon precursors reaching it from both the fetal and maternal compartments

Metabolitic function  The

primary function of the placenta is the transport of oxygen and nutrients to the fetus and the reverse transfer of CO2(carbon dioxide), urea, and other catabolites back to the mother.  These compounds are required for the synthsis of new tissues,eg,amino acids 、 vitamins and so on.  Substances such as certain maternal hormones, which may modify fetal growth.

Protective function  The

placental membranes are often referred to as a “barrier” to fetal transfer, but there are few substances(eg, drugs) that will not cross the membranes at all.

（ 2 ） The umbilical cord  In

the early stages, the embryo has a thick embryonic stalk containing 2 umbilical arteries,one large umbilical vein,the allantois （尿 囊） ,and primary mesoderm( 原中胚层 ).  At birth ， the mature cord : long 50-60cm diameter 12mm  A long cord is defined as more than 100cm and a short cord as less than 30cm.

（ 3 ） The amniotic fluid  In

the first of pregnancy,amniotic fluid volume appears to increase in association with growth of the fetus  Average volume 800ml

Amniotic fluid Source: early from serum dialysis( 透析 ) late from fetal urine Absorb: by fetal membrane, fetal swallowing(400-500ml/day) Umbilical cord Fetal skin Amniotic exchange: between maternal and fetal 400ml/h

Volume of amniotic fluid  8 weeks:5-10ml  10 weeks:30ml  20 weeks:400ml  38 weeks:1000ml

Note: After 38weeks, both amniotic fluid and maternal plasma volume decrease.

Status of amniotic fluid  pH:7.20  Density:1.007-1.025  Contained: water(98-99%)

inorganic substance( 无机

物) organic substance(1-2%)

The functions of amniotic fluid       

Cushions the fetus against severe injury Provides a medium in which the fetus can move easily Warm May be a source of fetal nutrients In early pregnancy,is essential for fetal lung development Protect mother Prevent infection

4 、 Maternal physiology during pregnancy  The

physiologic,biochemical,and anatomic changes that occur during pregnancy are extensive and may be systemic or local.  Those maternal adaptation maintain a healthy environment for the fetus.

Content:  Genital

tract

 Breasts  Cardiovascular

system  Hematologic system  Pulmonary system  Gastrointestinal tract

（ 1 ）、 Genital tract  Uterus  Ovaries  Vagina

and perineum

Changes of uterus Body: become enlargement and soft from 7×5 ×3cm pre-pregnancy to 35×25 ×22cm at term

Volume of uterus cavity: become enlargement from 5ml pre-pregnancy to 5000ml.at term

Weight: be increased from 50g prepregnancy to 1100g at term

Blood supply:blood flow increased significantly up to 450-650ml/min,increased 4-6 times and most of blood flow is transported to the placenta(80-85%)

Isthmus: be prolonged

and become soft from

1cm pre-pregnancy a portion of the uterus after 12 gestational weeks

Cervix: be soft and coloration or stain secrete amount of mucus avoiding the uterus cavity suffer from infection

Changes of ovary  Stop ovulation  Corpus luteum formation and maintains for

10 weeks  And the function of corpus luteum is

substituted by the placenta  Corpus luteum atretic gradually after 3-4

months gestation.

Vagina and perineum  During

pregnancy,increased vascularity and hyperemia develop in the skin and muscles of the perineum and vulva,and there is softening of the normally aboundant connective tissue( 结缔组织 ) of these structure.

（ 2 ）、 Breasts  In

the early weeks,the pregnant woman often experiences tenderness and tingling.  After the second month,the breasts increase in size and delicate veins become visible just beneath the skin.  After the first few months,a thick,yellowish fluid,colostrum,can often by expressed from the nipples （乳头） by gentle massage( 按摩 )

（ 3 ）、 Cardiovascular system  Heart  Cardiac

output  Blood pressure

Heart Heart border: become enlargement Heart rate: increased 10-15 beat per min at the late pregnancy

Heart volume: increased 10% at the late pregnancy

Cardiac output Very important for fetal growth and development

Increased begin 10 weeks and upto the peak at 32-34 weeks and continuing at this level until term Cardiac output increase approximately 40% during pregnancy

Blood pressure changes due to pregnancy  No obvious change in Systolic pressure  Mild decreased in diastolic pressure

Vein pressure  No significantly changes in Upper limb vein

pressure  Lower limb vein pressure increased because of

the disturbance of vein reflux （返流 ）

4 、 Hematologic system  Blood

volume  Blood components  Red blood cells  White blood cells  Clotting factors

Changes of blood system Volume: the average increase in volume at term is 45-50%. Hypervolemia begins in the frist trimester,increses rapidly in the second trimester,and the peak at about the 30th week.

Changes of blood components Red cell: the increase in red blood cell mass is about 33%,or approximately 450ml of erythrocytes( 红细 胞 ).Since plasma volume increases earlier in pregnancy and faster than red blood cell volume,after the end of second trimester( 妊娠期的 3 个月 ) : red cell decreased 3.6×1012(4.2×1012) Hb （ hemoglobin ） decreased 110g/L(130g/L)

 WBC(white

blood cell):the total blood leukocyte count increases during normal pregnancy from a pregnancy level of 4300-4500/uL to 5000-12000/uL in the last trimester.

Clotting factors: During pregnancy , level of several essential coagulation factors increase.There are marked increases in factorI 、 VII 、 VIII 、 IX 、 Xand XII .

(5) 、 Pulmonary system  Pregnacy

produces anatomic and physiologic changes that affect respiratory performance  Total lung capacity is reduced(4-5%)by the elevation of the diaphragm （膈肌）

(6) 、 Gastrointestinal tract  During

pregnancy,nutritional requirements are increased,and several maternal alterations occur to meet this demand

二、 Diagnosis of pregnancy  The

diagnosis of pregnancy is usually made on the basis of a history amenorrhea （闭 经） ,an enlarging uterus,and a positive pregnancy test

1 、 Diagnosis of the first-trimester pregnancy （早期妊娠）  History

and symptoms

 Signs  Assistant

examination

（ 1 ） History and symptoms ①Amenorrhea ：

It is a fairly reliable sign of conception in women with regular menstrual cycles. In women with irregular cycles,it is not a reliable sign. Delayed menses may also be caused by other factors such as emotional tension,chronic disease,endocrine disorders,and so on.

sickness （ nausea and vomiting ） :

②Morning

This common symptom occurs in approximately 50% of pregnancies. It begins at about 6 weeks’ gestation and disappears at about 12 weeks’ gestation in most patients. It is usually most severe in the morning but can occur at any time. The cause is probably rising serum levels of HCG.

③Bladder

frequency （尿频） :

It occurs because of increased bladder circulation and pressure from the enlarging uterus. It usually disappears after 12 weeks’ gestation when the uterus enlarges so much that it’s no longer a pelvic organ.

(2)Signs  Changes

in the genital organs  Changes in breasts A. Mastodynia( 乳房痛 ) B. Enlargement C. Linea nigra （色素沉着）

(3) Assistant examination  Pregnancy

test : urine testing  Ultrasound examination  Increased basal body temperature

①Pregnancy test  Sensitive early pregnancy tests measure changes in levels of HCG.  If maternal renal function is normal, urine values are usually proportionate to serum values.  Radioimmunoassay for HCG is a sensitive and specific test for early pregnancy.

②Ultrasound examination  It

is one of the most useful technical aids in diagnosing and monitoring pregnancy.  Cardiac activity is dicernible at 5-6weeks  Limb buds at 7-8weeks  Finger and limb movements at 9-10weeks  At the end of the embryonic period(10week by LMP), the embryo has a human appearance

③Increased basal body temperature  Persistent

elevation of basal body temperature over a 3-week period usually indicates pregnancy if temperatures have been carefully charted.

2 、 Diagnosis of the second and third-trimester pregnancy  Symptoms

and signs  Assistant examination

(1)Symptoms and signs enlargement  ②Quickening( 胎动 )  ③Fetal heart tones  ④Palpation( 触诊 ) of fetus  ①Uterine

①Uterine enlargement  At

16 weeks, the uterus is usually at the midpoint between the pubic and the umbilicus.  At 20 weeks ,the uterus is palpable at the umbilicus.  At 26-34 weeks, fundal height correlates roughly with the estimated gestational age.  But after 36 weeks, the fundal height may decrease as the fetal head descends into the pelvis.

②Quickening( 胎动 )  The

first fetal movement is usually appreciated at 17 weeks in the average multipara （经产妇） and at 18 weeks in the average primipara( 初产妇 ).

③Fetal  It

heart tones

may be heard at 20weeks.  The normal fetal heart rate is 120-160beats per minute.  It is best to palpate the maternal pulse for comparison.

④Palpation( 触诊 ) of fetus  After

20 weeks, the fetal outline can be palpated through the maternal abdominal wall.

(2)Assistant examination  Ultrasound

examination----ultrasound is used to measure fetal growth parameters, to estimate fetal weight, to access fetal anatomy, and to measure amniotic fluid volume.

3 、 Pregnancy monitoring  The

perinatal interval is the span of fetal and neonatal life.  The perinatal interval of life may be divided into 2 periods: Perinatal period I :28weeks of completed gestation to the frist 7days of life Perinatal period II: 20weeks of gestation through 27days of life

Prenatal care( 产前保健 )  The

purpose of prenatal care is to ensure,as much as possible, an uncomplicated pregnancy and the delivery of a live healthy infant.  Mothers and offspring who receive prenatal care have a lower risk of complications.

4 、 Initial office visit( 初诊 ) 1 ） History  （ 2 ） Physical examination  （ 3 ） Laboratory tests （

（ 1 ） History  Present

pregnancy ： The interview should begin with a full discussion of the symptoms; to determine the duration of pregnancy, the patient with regular menses may be able to accurately calculate the estimated date of confinement(EDC), using the first day of the LMP(LMP-3months+7 days)  Previous pregnancy :eg: events of prior pregnancies provide inportant clues to potential problems in the current one.

 Medical

history:eg: a history of cardiovascular 、 gastrointestinal , and endocrine disorders.  Surgical history ： eg ： a history of previous gynecologic surgery  Family history : eg ： history of diabetes mellitus

(2)Physical examination  General

examination( 一般检查 )  Pelvic examination （骨盆检查）

General examination( 一般检查 ) A

complete physical examination must be performed on every new patient.

Pelvic examination  Pelvic

soft tissue ： any pelvic mass should be described accurately and evaluated by Ultasound examination.  Bony pelvis :①pelvic inlet②midpelvis③pelvic outlet  Cervical length: average cervical length is 3-4cm

Laboratory tests The following laboratory assessments should be performed as early as possible in pregnancg and some of these repeated at least once between 24 and 36 weeks’ gestation:  Blood screening  Genetics testing  Urine testing

5 、 Subsequent visits The standard schedule for prenatal office visits is:  0-32week:once every 4weeks;  32-36weeks:once 2weeks;  36weeks to delivery:once each week  Weight, gain blood pressure, fundal height, findings on abdominal examination by Leopold’s maneuvers

6 、 nutrition in pregnancy  The

pregnant woman should be encouraged to eat a balanced diet and should be made aware of special needs for iron, folic acid, and zinc.

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